1. Field of the Invention
The present invention relates to absorbent articles such as diapers and particularly to water-in-oil emulsion concentrates as the absorbing material. More particularly, the present invention relates to absorbent articles which are capable of absorbing and retaining thereon large amounts of aqueous fluids such as urine in the form of a stable and highly viscous water-in-oil emulsion wherein the absorbing material is a concentrated water-in-oil emulsion forming composition carried on an oleophilic substrate.
2. Discussion of the Prior Art
Many attempts have been described in the patent literature to prepare super absorbent materials, i.e. materials which are capable of absorbing many times their weight of water or various body fluids. For example, the use of hydrogels for enhancing the absorbing media of absorbing articles, such as disposable diapers, has been described in U.S. Pat. Nos. 3,783,872 to King, 3,898,143 and 3,901,236 to Assarsson et al and 3,900,378 to Yen et al; Silane crosslinked acrylate interpolymers as the super absorbing media has been described in U.S. Pat. No. 4,062,451 to Gander; and various forms of modified starches have been described in the following U.S. Pat. Nos. 4,069,177 to Smith, 4,076,663 to Masuda et al, 4,115,332 to Young et al, and 4,117,222 to Holtz et al.
It is not believed, however, that the use of water-in-oil emulsion concentrates as the absorbing media, per se, have been described in the literature for this purpose. It is known, however, that water-in-oil emulsions can form viscous fluids with the viscosity increasing with increasing water content. The properties of emulsions have been extensively described in the literature and reference is made to the following publications: Becher, P., "Emulsions, Theory and Practice", Reinhold, New York, 1965 (Standard reference book on emulsions); Adamson A.W., "Physical Chemistry of Surfaces", 3rd Edition, John Wiley, New York, 1976 (Chapter 12 provides an overview of emulsions and foams); Prince, L.N., "Micro-Emulsions, Theory and Practice", Academic Press, New York, 1977 (review of modern emulsion technology); Lissant, K.J. and Mayhan, K.G., J. Colloid Interface Sci, 42, 201-208, January, 1973 (geometry of internal phase at high ratios); Groves, M.J., Chem. Ind. 12,417-423, June 17, 1978 (reviews recent concepts of spontaneous emulsification); Lin, T.J., et al, J. Soc. Cosmetic Chem. 26, 121-139, March, 1975 (Phase inversion temperature, HLB values and emulsion behavior).
There has also been patent literature of the use of mineral oils and mineral oil emulsions in various articles which are designed to come into contact with the human body. U.S. Pat. No. 3,264,188 to Gresham describes a sanitary impregnated tissue for proctological use in which a pure pharmaceutical grade mineral oil of low viscosity containing a fatty acid soap of an organic base as a non-toxic, non-allergenic emulsifier is impregnated throughout one or more plies of absorbent creped cellulosic tissue. This tissue is described as having ability, when used as a wipe, to pick up, absorb, and hold fecal matter from the skin and wiped areas while transferring a thin film of the emulsifier-containing mineral oil to the skin.
U.S. Pat. No. 3,464,413 to Goldfarb, et al describes absorbent dressings having a multiplicity of discrete rupturable microcapsules containing various agents including emulsified oils. U.S. Pat. No. 3,489,148 to Duncan, et al describes a diaper having an absorptive pad and a thin diaper fibrous material top sheet. On one face of the top sheet a discontinuous film of an oleaginous moisture barrier material is applied to at least the central portions thereof for application to the skin of an infant. The patentee teaches that mineral oil can be mixed with a crystalline material such as triglycerides of higher fatty acids to increase its viscosity. A diaper containing pressure rupturable capsules containing formulations based on mineral oil and other ingredients such as isopropyl myristate is described in U.S. Pat. No. 3,585,998 to Hayford, et al.
U.S. Pat. No. 2,653,601 to E. M. Morrison relates to gloves designed and intended for use as an accessory for the treatment of the skin of the hands of the wearer. The glove includes a relatively heavy layer of a porous material including sheet rubber or lightweight plastic. The porous material is adapted to hold within its pores or interstices a cream or lotion. However, in practice, the cream or lotion is placed on the hands of the wearer and the glove primarily provides a massaging function.
U.S. Pat. No. 3,896,807 to Buchalter relates to an article such as a piece of apparel, e.g. glove, or an applicator pad, impregnated with the oil phase of a cream formulation which upon the addition of moisture thereto forms a skin-soothing cream. This patent also mentions other patents disclosing articles of apparel and applicator pads for use in applying therapeutic creams, lotions or oils to the skin. In this patent the oil phase is in the form of a dry non-oily solid including from about 1 to 99% of an oily material and from about 99 to 1% of an emulsifier. When the oil phase impregnated in the articles is mixed with water a cream or a less viscous lotion is formed. Either water-in-oil or oil-in-water emulsions may be formed.